Mechanically evaporated salt
Mechanically evaporated salt is also made from seawater, but it is heated mechanically rather than evaporated in the sun. Because the heat levels are controlled, they are more precise and effective at killing bacteria.
While this method kills bacteria and microorganisms, it also creates a very mineral-rich salt, which contains pure salt mixed with calcium, magnesium, copper, nitrite and other minerals.
None of these elements are good to put in your pool. Most of the above elements do not affect the cleanliness of the water but rather its balance. They can also affect your salt cell and stain your pool.